Semiconductor components, in particular diaphragm sensors and methods for manufacturing diaphragm sensors on the basis of semiconductor substrates, silicon wafers, for example, are known. A flat porous diaphragm area, for example, is placed on a semiconductor substrate as a substrate layer for sensor structures, and subsequently a clearance for insulating, e.g., thermally, the diaphragm is produced by removing the porous layer (sacrificial layer) underneath the diaphragm.
The conventional diaphragm sensors are mostly implemented as thin-layer diaphragm sensors. Initially layer systems having a thickness between tens of nanometers and a few μm are deposited onto a substrate, whereupon the substrate is removed in predefined areas to obtain unsupported diaphragm areas. Sensor structure elements may then be placed in the diaphragm center.
Another possibility for exposing the diaphragm is surface micromechanics, in which a sacrificial layer is normally used, which is applied to the front of a substrate prior to depositing the diaphragm. The sacrificial layer is then removed from the front of the sensor through openings in the diaphragm, whereby an unsupported structure is obtained. These surface micromechanical methods are relatively complex due to the need for separate sacrificial layers.
Published German Patent Application No. 100 32 579 describes a method for manufacturing a semiconductor component and a semiconductor component manufactured according to this method, in which a layer made of porous semiconductor substrate material is placed over a cavity. Two layers of different porosities are produced using appropriate etching parameters for producing the cavity. The first layer has a lower porosity, during a subsequent first heating step the porosity of the second layer increases during the heating step in such a way that a cavity is formed. A relatively thick epitaxial layer is grown as a second diaphragm layer at a higher heating temperature in a second process step on the first diaphragm layer thus formed from the first porous layer.
As an extension of the method described in German Patent Application No. 100 32 579, a thin epitaxial layer may also be grown during the first heating step to ensure that the porous first layer, which is used as the start layer for the epitaxial growth of the thick epitaxial layer, is completely closed. A lower growth rate at a lower temperature is preferably selected here compared to the subsequent deposition of the thick epitaxial layer.
The above-mentioned measures are used to simplify the structure of a surface micromechanical semiconductor component, because no additionally applied sacrificial layer is needed, and the diaphragm itself or a substantial portion of the diaphragm is produced from semiconductor material.
To prevent damage to the diaphragm during the manufacturing process or during regular use, published German Patent Application No. 101 38 759 provides a method for manufacturing a semiconductor component having a semiconductor substrate, in which the semiconductor substrate receives a type of doping in the area of the porous diaphragm layer that is different from that in the area of the future cavity. After doping, the semiconductor material of the diaphragm layer is made porous and the semiconductor material underneath the porous semiconductor material is at least partially removed or displaced to provide a cavity.
German Patent Application No. 103 58 859 describes a method which is an extension of the method described in published German Patent Application No. 101 38 759. As described in German Patent Application No. 103 58 859, a porous layer is produced underneath areas of non-porous semiconductor material. An epitaxial step is subsequently carried out, in which an epitaxial layer, which forms the future diaphragm, closes the surface starting at the non-porous areas. Finally, a cavity is produced from the porous layer using a thermal treatment.